Objective-C binding for ZeroMQ.
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objc-zmq is an Objective-C binding to ZeroMQ

This is an Objective-C version of the reference ZeroMQ [object-oriented C API][zmq-docs]. It follows the guidelines laid out by the official ["Guidelines for ZeroMQ bindings"][binding-zmq].

[zmq-docs]: http://api.zeromq.org/zmq.html (zmq(7) Manual Page) [binding-zmq]: http://www.zeromq.org/docs:bindings (Guidelines for ZeroMQ Bindings)


To run the example project; clone the repo, and run pod install from the Project directory first.


  • OSX 10.9 (Mavericks)
  • Xcode 5.0.2


objc-zmq is not yet available through CocoaPods.

To install it simply add the following line to your Podfile:

pod "objc-zmq", :git => 'https://github.com/jeremy-w/objc-zmq.git'


objc-zmq is available under the MIT license. See the LICENSE file for more info.


Refer to the [ZeroMQ manual pages][zmq-docs].

The Objective-C binding maintains a bit more state than the C API exposes, in that you can query a ZMQContext for its sockets and query a ZMQSocket for its context.

Thread Safety

Early versions of ZeroMQ had some restrictive thread safety and coupling issues:

  • Sockets can only be used from the thread that created them.
  • All ZMQ sockets provided in a single call to zmq_poll() must have been created using the same context.

Because sockets are coupled to contexts for polling, you have to track each socket's context and make sure not to mix them. (The ZMQSocket class tracks this for you.) This is not as restrictive as it sounds, because most applications will only ever use a single context.

Prior to version 2.1.0, each socket was permanently bound to the thread that created it. This made it very difficult to use ZeroMQ sockets with Grand Central Dispatch or NSOperationQueue, because the only persistent thread that these two APIs expose is the thread you're least likely to want to perform socket operations on: the main thread.

Starting with version 2.1.0, a socket can be used from different threads provided a full memory barrier, such as that introduced by <libkern/OSAtomic.h>'s OSMemoryBarrier function, separates the socket's use on one thread from its use on another.

To Do

  • Add functional tests in the form of sample code.
  • Tie polling into the runloop, similar to NSStream, CFSocket, or CFFileDescriptor.